B-stage polyurethane compositions

ABSTRACT

CURABLE B-STAGE POLYURETHANES SUITABLE FOR USE AS INTERLAYERS FOR GLASS LAMINATES COMPRISE THE REACITON PRODUCT OF AT LEAST ONE HYDROXY-CONTAINING ESTER HAVING A TERMINAL ACRYLYL OR SUBSTITUTED-ACRYLYL GROUP, AN ORGANIC DIISOCYANATE AND A POLYOL. THE COMPOSITIONS ARE STABLE AT ROOM TEMPERATURE EVEN WHEN CONTAINING A FREE RADICAL PRODUCING INITIATOR BUT CURE IN THE PRESENCE OF FREE RADICALS TO A HARD, THERMOSET STATE. THE PREFERRED DIISOCYANATES INCLUDE ISOCYANATO-TERMINATED POLYETHER ADDUCTS OF POLY(OXYPOLYMETHYLENE) GLYCOLS.

United States Patent O 3,823,051 B-STAGE POLYURETHANE COMPOSITIONSWen-Hsuan Chang, Gibsonia, Pa., assignor to PPG Industries, Inc.,Pittsburgh, Pa.

No Drawing. Application May 6, 1970, Ser. No. 35,286,

which is a continuation-in-part of abandoned application Ser. No.746,739, July 23, 1968. Divided and this application June 20, 1972, Ser.No. 264,656

Int. Cl. B32b 17/10, 27/40 US. Cl. 156-99 5 Claims ABSTRACT OF THEDISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION This is a division ofapplication Ser. No. 35,286, filed May 6, 1970, now abandoned, whichapplication is a continuation-in-part of copending application Ser. No.746,739, filed July 23, 1968, now abandoned.

BACKGROUND OF THE INVENTION Glass laminates, i.e. laminates of plates orsheets of glass bonded to an interlayer material, are widely used inglass areas of automobiles, aircraft and the like, as well as in certainarchitectural applications. For the most part, such glass laminates aremade using polyvinyl butyral in sheet form as the interlayer materialand they are produced using high temperatures and high pressurelaminating techniques. Not only are such laminating techniques difiicultand cumbersome, but the thermoplastic interlayers, such as polyvinylbutyral, employed therein often do not meet the level of performancewhich is desired to provide optimum safety during use of the article.

Other types of interlayer materials have been developed which providesafety glass of highly desirable characteristics and which can beapplied by other methods, such as by a cast-in-place procedure. However,such materials have also been subject to certain disadvantages includingthe need for rigid control of the casting process because of the shortpot life of the materials employed.

The present invention overcomes these diflicnlties by the use of aneasily handled resinous polyurethane which provides a glass laminate ofsuitable properties but which can be utilized by procedures analogous tothose employed with the thermoplastic materials of the prior art, butwhich in many cases avoids the need for severe laminating conditions.

Hydroxyalkyl esters of unsaturated acids have been employed inpolyurethane compositions heretofore. For example, polymers andcopolymers of hydroxyalkyl acrylates and methacrylates have been reactedwith polyisocyanates to produce polyurethanes for castings, coatings,and the like. However, such reaction products differ from those hereinin that they are fully cured reaction with the polyisocyanate and thusare subject to the same disadvantages, such as short pot life, which areencountered with the other materials suggested for cast-in-placeapplications heretofore.

BRIEF SUMMARY OF THE INVENTION The invention herein provides durableB-stage resinous polyurethanes which comprise the reaction product ofone P KB or more hydroxyl-containing esters having a terminal acrylyl oralpha-substituted acrylyl group with an organic diisocyanate and apolyol. The reaction product is an ungelled material corresponding tothe formula where X is the radical derived by removing a hydroxylhydrogen atom from the hydroxyl-containing ester having a terminalacrylyl or alpha-substituted acrylyl group, R is a divalent organicradical, R is hydrogen or an organic group containing urethane linkages,Y is a radical derived by removing the hydroxyl groups from a polyolhaving n hydroxyls, n is a number greater than one and up to about 8,and m is a number greater than one and up to about 4.

This product can be further cured to a hard, thermoset state in thepresence of free radicals such as are produced by heating to hightemperatures, or more usually, by the use of free radical initiators.The composition may include a peroxide or other free radical initiatorand such mixtures are stable at temperatures up to the temperature atwhich the initiator decomposes to produce free radicals.

DETAILED DESCRIPTION OF THE INVENTION As stated above, the inventioncomprises the reaction product of three essential components, namely,one or more hydroxyl-containing esters having a polymerizable ethylenicgroup, an organic diisocyanate, and a polyol.

The ester component can be any monomeric ester or polyester containingat least one hydroxyl and a terminal acrylyl or alpha-substitutedacrylyl group. Useful monomeric esters include hydroxyalkyl esters ofacrylic acid or alpha-substituted acrylic acids, such as methacrylic.

acid and alpha-chloroacrylic acid. Especially preferred esters areacrylic acid and methacrylic acid esters of ethylene glycol, i.e.hydroxyethyl acrylate and methacrylate and hydroxypropyl acrylate andmethacrylate. However, there may also be employed similar esters ofalpha-substituted acrylic acids, such as ethacrylic acid, crotonic acidand similar acids having, for example, up to about 6 carbon atoms, aswell as corresponding esters containing other hydroxyalkyl radicals,such as hydroxybutyl esters and hydroxylauryl esters.

Also useful are substituted hydroxyalkyl esters of the above unsaturatedacids, such as, for example, l-acryloxy- 3-phenoxy-2-propanol, which canbe produced by reacting phenyl glycidyl ether with acrylic acid. Othercompounds of this type and other substituted hydroxyalkyl esters, suchas, for example, hydroxyalkyl acryloxyalkyl phthalates or maleates, canalso be utilized.

Hydroxyl-containing polyesters having terminal acrylyl oralpha-substituted acrylyl groups are also included. These can beproduced, for example, by reacting one mole of acrylic or methacrylicacid with two moles of a dicarboxylic acid, such as adipic acid, azelaicacid, or other such acid, and three moles of a diol such as ethyleneglycol, 1,4-butanediol, or the like. Similar polyesters can be producedusing other such reactants in varying proportions, so long as asubstantially linear product having residual hydroxyls and an acrylyl orsubstituted acrylyl group is provided.

The organic diisocyanate which is reacted with the ester component canbe essentially any diisocyanate, i.e., hydrocarbon or substitutedhydrocarbon diisocyanates and isocyanato-terminated adducts of polyols.Many such organic diisocyanates are known in the art.

Among the organic diisocyanates which can be employed are arylenediisocyanates, such as p-phenylene diisocyanate, diphenyl diisocyanateand the like; alkarylene diisocyanates, such as toluene diisocyanate,3,3'-dimethyl- 4,4-biphenylene diisocyanate and the like; alkylenediiso+ cyanates, for example, 1,4-tetramethylene diisocyanate,

hexamethylene diisocyanate, 2,2,4-trimethylhexane 1,6-di-- isocyanate,etc.; aralkylene diisocyanates, such as methylenebis(phenylisocyanate);and alicyclic diisocyanates, for example, isophorone diisocyanate andmethylcyclohexyl diisocyanate.

Other diisocyanates that can be employed are isocyanato-terminatedadducts of diols such as ethylene glycol, 1,4-butylene glycol,polyoxyalkylene glycols, etc. These are formed by reacting two moles ofa diisocyanate, such as those mentioned above, with one mole of a diol.

One preferred class of organic diisocyanates comprises prepolymersproduced from an organic diisocyanate such as toluene diisocyanate witha poly(oxypolymethylene) glycol. Representative poly(oxypolymethylene)glycols of this group contain oxypolymethylene groups in which a linearchain of from about 2 to about 6 carbon atoms separate each adjacentpair of oxygen atoms. Preferred are poly(oxytetramethylene) glycols.Other polyether glycols, such as poly(oxypentamethylene) glycols andpoly(oxyhexamethylene) glycols, can also be used but are usually lessdesirable as a class, as are branched carbon chain compounds. It isdesirable that the poly(oxypolymethylene) glycol have a molecular weightbetween about 100 and about 4000, although the optimum molecular weightvaries with the particular system and the intended use for the product.

Other useful diisocyanates include isocyanate-terminated adductsproduced from polyesters polyols, such as adducts of various saturatedand unsaturated polyester polyols made from esterification of polyolsand dibasic acids and containing unreacted hydroxyl groups. An exampleis the reaction product of toluene diisocyanate with a polyester formedfrom propylene glycol and adipic acid. Such polyester adducts arewell-known and are utilized in the manufacture of conventional types ofpolyurethane products.

In many cases, more than one diisocyanate is employed; for example,toluene diisocyanate or other low molecular weight diisocyanate is oftenadded along with an isocyanato-terminated prepolymer, or severalprepolymers of varying molecular weights are used. This permitsformulation of the product to provide a desired level of hardness,flexibility and similar properties.

The polyol which is employed can be any monomeric or polymeric polyolhaving an average of more than one hydroxyl group and up to about 8hydroxyls per molecule. Useful polyols include ethylene glycol,1,4-butanediol, 1,6- hexanediol and other alkylene glycols, glycerine,sorbitol, cyclohexane dimethanol, hydrogenated Bisphenol A, and thelike, as well as polymeric polyols, including polyether polyols such aspoly(oxypolymethylene) glycols, oxyalkylated sucrose or other polyol,copolymers of allyl alcohol and styrene, hydroxyl-containing epoxyresins or epoxy esters, polyesters having free hydroxyls, and the like.In many cases a mixture of polyols is utilized.

Optional ingredients which can be included in the overall compositioninclude small amounts of higher polyols; chain transfer agents, such asmercaptans; small amounts of monohydric alcohols, including in somecases a hydroxyalkyl ester of a saturated carboxylic acid;copolymerizable monomers, such as styrene, acrylates, etc. and otheradditives such as inhibitors, antioxidants, stabilizers and the like.

The components are combined in proportions chosen so as to avoidgellation of the product, i.e. to provide an ungelled product which issubstantially linear. The proportions employed depends uponconsiderations well known to those in the art, such as the funcitonalityof the particular reactants and their reactivity with each other. Thenumber of isocyanate groups should be not greater than the total numberof hydroxyl groups present, and preferably the diisocyanate is employedin an amount which provides substantially equivalent amounts of hydroxyland isocyanato groups. The diisocyanate reacts in part with the polyoland in part with the hydroxyl group of the ester; in some cases theisocyanate may react with excess hydroxyls of the polyol to provide acoupled product.

The reaction to produce the B-stage polyurethane takes place uponadmixture of the components, although moderate heating is generallyutilized in order to insure complete reaction within a reasonableperiod. In some instances, such as when an aliphatic diisocyanate isemployed, a catalyst is desirable to promote the urethane-formingreaction. Dibutyltin dilaurate, zinc octoate and the like are examples.Temperatures below about C. are ordinarily employed. The product is aB-stage resin which can be easily handled and which is essentiallythermoplastic, provided the curing conditions as described below are notencountered. Thus, it can be heated to a fluid state and cast or spreadupon a substrate, or it can be employed in coatings in solution or as asolventless coating material.

The B-stage polyurethane produced in the foregoing manner has the majorresinous component product corresponding generally to the averageformula In the above formula, X is an organic radical formed by removinga hydroxyl hydrogen atom from an ester containing an acrylyl oralpha-substituted acrylyl group and at least one hydroxyl group. Theradical represented by X is the residue of the ester component describedabove after reaction of the hydroxyl group, and thus can be derived fromany of the monomeric esters or polyesters described.

In the peferred embodiment in which the ester employed is a hydroxyalkylester of an acrylic acid, the product has the average formula R O 0 O(HzC:J-PJ-ORz0&-NHR1NH( -OT-Y(OR) where R is hydrogen or lower alkyl,e.g., methyl, and R is an alkylene or substituted alkylene of at least 2carbon atoms, derived from the hydroxyalkyl group of the ester. Thegroup represented by R may be an alkylene group substituted with alkoxy,aryloxy, oxyalkylene and other such groups.

In the embodiment in which an acrylyl-terminated hydroxyl-containingpolyester is utilized, the product has the formula (III) (x-m-oii-nrii-o-Ih-o -NHIh-NH i J0/-Y(o 10,-...

where R is an alkylene or oxyalkylene group such as those represented byR and R is a divalent organic radical, such as alkylene, arylene, oralkenylene, or a polyester moiety. Products of this type are produced,for example, by employing as the ester component a reaction product ofone mole of hydroxyethyl acrylate, one mole of phthalic anhydride andone to two moles of ethylene oxide, or the product from the reaction ofone mole of methacrylic acid, two moles of adipic acid and three molesof 1,6-hexanediol.

The group represented by R in the above formulas is derived from thediisocyanate and thus can be essentially any divalent organic radical.For example, R; can be arylene, alkylene, alkarylene, aralkylene,alicyclic, oxyalkylene, etc., including halogen or other substitutedgroups, depending upon the organic diisocyanate employed, as illustratedby the varied types of diisocyanates mentioned above. In many cases thepolyurethane is chainextended and contains urethane linkages.

The radical represented by Y is the residue of the polyol without thehydroxyl groups, and thus also can be of widely varying structures. Asindicated by the polyols described above, Y can be monomeric orpolymeric and can be of essentially any organic structure which can havehydroxyl groups attached thereto.

As described above, Y is derived from a polyol having n hydroxyl groups,where n is a number greater than one and up to about 8. Since theformula given is an average formula, and a mixture of polyols can beutilized, n can be a whole or fractional number.

In producing the curable polyurethane, the number of polyurethane groupsterminated with radicals containing acrylyl or substituted acrylylgroups is greater than one but not more than about 4 (designated by m).The remaining hydroxyls of the polyol, if any, are represented by OR,where R is hydrogen if the hydroxyls remain unreacted or aurethane-containing organic radical where the hydroxyl is reacted with adiisocyanate, which may be the same or different as that used to producethe X-terminated groups. The groups represented by R, however, do notcontain an acrylyl or substituted acrylyl group as does that representedby X.

The B-stage product described above is resinous but remainsthermoplastic; it cures by addition polymerization in the presence offree radicals to a hard, thermoset state. The free radicals can beprovided by a free-radical producing initiator which can be included inthe polyurethane composition as formed, or which can be added at a latertime. Such initiators are most often organic peroxides such asdi(tertiary-butyl) peroxide, which is a preferred initiator, cumenehydroperoxide, dicumyl peroxide, peracetic acid, methylethyl ketoneperoxide, benzoyl peroxide and the like. Other free radical-producinginitiators, such as azo compounds, e.g., alpha,alpha'-azobis(isobutyronitrile) orp-methoxyphenyl-diazothio(Z-naphthyDether, can also be utilized. Inaddition to curing of the product by the inclusion of free radicalinitiators, curing can also be effected by other means, for instance byheating to sufficiently high temperatures, or by irradiation using anelectron beam or ultra-violet light.

Using peroxides or other free radical producing initiator, the curing iscarried out at temperatures suflicient to pro vide free radicals fromdecomposition of the initiator at a reasonable rate. In the case ofdi(tertiarybutyl) peroxide, for example, the products generally cure atfrom 200 to 400 F. Where a free radical-initiator such as a peroxide isutilized, the amount is usually at least about 0.01 percent of theyoverall composition and is generally within the range of from about 0.01percent to about 3 percent.

Safety glass laminates are produced by applying the B- stage material toat least one layer of glass and curing the B-stage material While incontact with the glass. The type of glass employed is not critical andcan be of any composition to provide the desired optical and strengthproperties. conventionally, two or more layers of glass are bondedtogether using these materials as the interlayers, but laminates canalso be produced using a single layer of glass or using one or moreglass layers together with one or more layers of hard, transparentplastic material. Acylic polymers such as poly(methyl methacrylate) andpolycarbonates such as those described in US. Pat. 3,117,- 009' aresuitable plastic materials. The laminates produced are strong and clearand have those properties necessary for an acceptable glass includingexcellent adhesion, high impact resistance, clarity and the like.

The invention will be further described by reference to several exampleswhich follow. These examples are illustrative and should not beconstrued so as to limit the invention to their details. All parts andpercentages are by Weight unless otherwise specified. Where toluenediisocyanate is employed in the examples there was used the ordinarycommercial mixture of 80 percent 2,4-isomer and 20 percent 2,6-isomer.

Example 1 Parts by weight Prepolymer A 222.3 Prepolymer B 31.8 Toluenediisocyanate (Hylene TM) 45.9 Substituted benzotriazole U.V. lightabsorber (Tinuvin P) 0.3 Methyl acid phosphate 0.3

This mixture Was heated to F. and stirred under vacuum to removedissolved gases. A second mixture of the following composition wassimilarly degassed at room temperature:

Parts by weight 1,4-Butanediol 39.6 2-Hydroxyethyl acrylate 6.0Di(tertiary-butyl) peroxide 0.06

The second mixture was added to the reaction vessel and stirred for 5minutes; the temperature rose from 125 F. to 182 F. The mixture was thenpoured into a casting cell made of two 12 inch by 12 inch Teflon coatedglass plates spaced 60 mils apart with a silicone gasket and spaceraround the periphery. The casting cell was preheated to 200 F.; thefilled cell was heated at 200 F. for 4 hours and cooled. The product wasa clear, transparent strong sheet having a Shore A hardness (roomtemperature) of 58; it has excellent storage stability. This sheet wasemployed in making a safety glass laminate by placing it between two 12inch by 12 inch sheets of inch thick plate glass, and laminating theassembly in an autoclave at 265 F. and 200 p.s.i. for 30 minutes. Thelaminate obtained had good optical and strength properties; for example,its impact resistance, as measured by dropping a five-pound steel ballonto laminates prepared using the above formulation as the interlayerfrom various heights to determine the maximum height from which the balldoes not pass through the laminate, was 4 feet at 0 F. and 7 feet at 120F.

Example 2 Following the procedure of Example 1, a B-stage resin wasproduced from the following:

Parts by weight The thermoplastic sheet obtained (about inch thick) wascut into strips approximately /2 inch wide and extruded through a inchextruder fitted with a 2 /2 inch by 0.020 inch film die at a screw speedof 20 rpm. and an average temperature of about F. The resin extrudedsatisfactorily to a slightly cloudy sheet 35 mils thick at the edges and41 mils thick in the center. This sheet was embossed with fine lines (toremove air) and then placed between 12 inch by 12 inch glass plates. Theassemblies were heated for 30 minutes at 300 F. under vacuum and thenheated in an autoclave at 275 F. and 200 psi for 45 minutes. Thelaminate obtained was clear with a slight haziness and had propertiescomparable to those of the product of Example 1.

7 Example 3 Example 2 was repeated using a resin of the followingcomposition:

Parts by weight Prepolymer A 824.6 Toluene diisocyanate 175.41,4-Butanediol 130.7 Trimethylol propane 7.7 Z-Hydroxyethyl acrylate20.0 Di(t-butyl) peroxide 0.2

The product obtained had similar properties to that of Example 2.

Examples 4-6 Following the procedure of Example 1, several laminateswere made utilizing resins of varying composition. The laminates had aninterlayer about 30 mils thick. The data are shown below:

Example 4 5 6 Prepolymer:

B Toluene diisocyanate lA-butanediol 'Iri methylolpropaneTrimethylolpropane monoallyl eth 2-hydroxyethyl acrylate 2-hydroxypropylacrylate 10. 3 2-hydroxyethyl methacrylate 22. 9 Subs. benzotriazole(U.V abso ber 0.6 0.6 Methyl acid prospl1ate. 0.5 0.6 0. 6 Di(t-butyl)peroxide. 1. 5 0.12 0.09 Impact resistance:

F. it 2% 5 (120 F.), it 8 12 7 Example 7 Example 1 was repeated usingthe following: Prepolymer A 247.4 Pepolymer C 245.2 Toluene diisocyanate77.4 1,4-Butanediol 84.0 2-Hydroxyethyl acrylate 12.0 Methyl acidphosphate 0.6 0.12

Di(t-butyl) peroxide Prepolymer C was produced by reacting 652.5 partsof toluene diisocyanate with 1280 parts of polypropylene glycol havingan average molecular weight of 1025. The laminate obtained was suitablefor some purposes but its properties were somewhat inefrior to thoseabove.

Example 8 Following the procedure of Example 1, a laminate was producedusing the following:

2-Hydroxypropyl acrylate Di(t-butyl) peroxide 0.008

A clear useful laminate was obtained; however, its strength was belowthat of Example 1.

Example 9 In this example there was employed a polyester glycol preparedfrom 2 moles of maleic anhydride, 3 moles of neopentyl glycol and 1 moleof acrylic acid. The following were employed to produce B-stagepolyurethanes (materials in parts by weight):

A B C Polyester glycol 20 20 Toluene diisocyanate 5 3 10 Butyl acrylate.2 1 3 1,4-but-anediol 10 10 10 The reactions were carried out by heatinga mixture of the polyester glycol and toluene diisocyanate in butylacrylate in the presence of a trace of dibutyl tin diacetate for 4 hoursat 200 F., then adding the 1,4-butanediol and allowing the mixture tostand at room temperature overnight. The B-stage products obtained hadessentially no unreacted NCO groups and were clear, viscous yellowishliquids. Each was cured by adding 20 percent by weight of benzoylperoxide and heating at 200 F. for 30 minutes. The cured products wereclear, hard and strong, although brown in color.

Example 10 In this example there was employed an acrylylterminated esterproduced from phthalic anhydride, 2- hydroxyethyl acrylate and ethyleneoxide and having the formula A mixture of 52 parts of the above ester,18.3 parts of toluene diisocyanate and 34.7 parts of polyester polyol(made from 1 mole of adipic acid, 1.1 mole of neopentyl glycol and 0.02mole of trimethylolpropane), in 26.6 parts of butyl acrylate, werereacted as above to produce a B-stage polyurethane, which was cured bythe addition of 2 percent by weight of benzoyl peroxide and heating at200 F. for 15 minutes.

Example 11 One mole of the diglycidyl ether of Bisphenol A (Epon 828)was reacted with 2 moles of acrylic acid to give an acrylyl-terminatedester, which was dissolved in a 3 to 1 ratio of butyl acrylate andtriethylene glycol at percent solids. A mixture of 12 parts of thissolution and 11.3 parts of toluene diisocyanate in 7.5 parts of butylacrylate were reacted to form a B-stage polyurethane which was curableto a hard thermoset state in 1 hour at 200 F. in the presence of 0.1percent by weight of benzoyl peroxide.

According to the provisions of the patent statutes, there are describedabove the invention and what are now condidered to be its bestembodiments. However, within the scope of the appeded claims, it is tobe understood that the invention can be practiced otherwise than asspecifically described.

I claim:

1. A method of producing a glass laminate which comprises the steps of:

(A) admixing one or more hydroxyl containing esters having a terminalacrylyl group or alpha-substituted acrylyl group, an organicdiisocyanate, and a polyol to produce a curable, substantially linearB-stage polyurethane resin corresponding to the average formula:

where X is an organic radical formed by removing a hydroxyl hydrogenatom from an ester containing a terminal acrylyl or alpha-substitutedacrylyl group and at least one hydroxyl group, R is a divalent organicradical, R is hydrogen or an organic group containing urethane linkages,Y is a radical derived by removing the hydroxyl groups from a polyolhaving n hydroxyl groups, n is a number greater than 1 and up to about8, and m is a number greater than 9 10 1 and up to about 4, wherein saidB-stage poly- Refer Cit d urethane, while being curable to a hardthermoset state by addition polymerization, is essentially UNITED STATESPATENTS thermoplastic; 3,522,142 7/1970 WiSlIlfil' et al (B) applyingaid B-stage polyurethane to a su f f 5 3,297,745 1/1967 Fekete et a1.260-471 at least one sheet of glass; and 3,425,988 /1969 Gorman 260-47(C) curing the applied B-stage polyurethane by addi- 3,539,424 11/ 1970Tas lck 15623-8 i polymerizatiom 3,330,713 7/1967 Watson et al. 1562442. The method of Claim 1 in which said B-stage poly- 3,697,622 10/1972K6111 260858 urethane is in sheet form. 10 3,458,333 7/1959 M ymhan16l65 a. The method of Claim 1 in which said polyurethane 3,422,1651/1969 Br therton et a1. 260-859 is cured by heating in the presence ofa free-radical 3,711,364 1/1973 Ahramiian 6-99 initiator. 3,580,7965/1971 Hick, Jr. et a1. 161-190 4. The method of Claim 3 in which saidfree-radical initiator is n organgcvperoxidm 15 DANIEL J. FRITSCH,Pl'lmal'y Examiner 5. The method of Claim 1 in which said polyurethaneis cured by irradiation with an electron beam or ultra- US violet light.156--106, 272, 331; 161--19O

